1. Technical Field
Example embodiments of the present invention relate to a method and apparatus monitoring oxygen sensor operation for an internal combustion engine.
2. Related Art
As a part of the monitoring systems in a modern internal combustion engine, the response characteristics of the oxygen sensors are monitored to ensure the correct operation of the sensors. A known response monitor for a heated exhaust gas oxygen (HEGO) sensor can be operable to monitor the HEGO response during fuel cut (FC) operation. A fuel cut operation can, for example, be triggered when one or more or all cylinders in the engine have entered into fuel cut. In some known systems, fuel cut is entered on a sequential cylinder basis. This means that the fuel cut does not occur on all cylinders at the same time. Instead, individual cylinders enter fuel cut with a calibratable delay. In this known system, the next cylinder to enter fuel cut is not deterministic, which means that any cylinder across cylinder banks can be selected as the next cylinder to enter fuel cut depending on the engine speed. This slow and/or random operation means that a robust HEGO response diagnostic is difficult to achieve.
There is a need to provide a robust approach to the monitoring of a sensor response in a fuel cut situation.